code: def test_transformer_stack_with_cross_attention(params):
      params["add_cross_attention"] = True
  
      transformer_stack = TransformerStack.from_params(params).eval()
      modules = dict(transformer_stack.named_modules())
  
      assert hasattr(modules["layers.0"], "cross_attention")
  
      attention_mask = torch.tensor([[0, 1, 0], [1, 1, 0]])
      transformer_stack.forward(
          torch.randn(2, 3, 6),
          attention_mask=attention_mask,
          encoder_hidden_states=torch.randn(2, 3, 6),
      )
  
file_path: allennlp/tests/modules/transformer/transformer_stack_test.py
imports: import copy
  import torch
  import pytest
  from allennlp.common import Params
  from allennlp.common import cached_transformers
  from allennlp.modules.transformer import TransformerStack, TransformerLayer
label_desc: Use image node_id 3 for calling a global function with example usage: test_transformer_stack_with_cross_attention(params) without return types